Production of texturised yarn

ABSTRACT

A process for producing bulk is described by sequentially drawing and false twist texturizing a synthetic yarn wherein the yarn is withdrawn from the texturizing zone at a greater speed than it is fed thereto. In a preferred embodiment, the draw roll for the drawing step also serves as the take-off roll for the texturizing zone and is stepped so that the portion used to take off the texturized yarn is of greater diameter than the part used for drawing. A further preference is that the heater in the texturizing zone is a heated pin.

United States Patent 119 Doschko et al.

1451 Aug. 13, 1974 1 PRODUCTION OF TEXTURISED YARN [75] Inventors:Werner Doschko, NuBloch, Am

Leimbach; Hermann Rinklin, Oestringen, both of Germany [73] Assignee:Imperial Chemical Industries Limited, London, England [22] Filed: Nov.6, 1972 [21] Appl. No.: 304,033

[30] Foreign Application Priority Data Nov. 17, 1971 Great Britain53300/71 July 13, 1972 Great Britain 32813/72 52 us. (:1. 57/34 ns,57/51.6, 57/157 TS, 57/157 MS, 57/56 511 1m. 01 D02g 1/02 58 Field 61Search 57/1 R, 34 R, 34 11s, 36, 57/51,51.6, 157 R, 157 5,157 MS, 157TS,

[56] References Cited UNITED STATES PATENTS 2,936,567 3/1960 Russell eta1 57/77.4

3,041,814 7/1962 Held 57/34 HS 3,069,837 12/1962 Olson 57/34 HS X3,178,795 4/1965 Warthen 57/34 HS X 3,365,874 1/1968 Chidgey et a1.57/157 TS 3,432,355 12/1947 Truitt 57/157 S X 3,645,081 2/1972 Salama57/34 HS 3,651,633 3/1972 Stcinmiller 57/157 TS X 3,729,916 5/1973 Lusket a1. 57/34 HS Primary Examiner-Donald E. Watkins Attorney, Agent, orFirmHerbert M. Adrian, Jr.

[ 5 7] ABSTRACT A process for producing bulk is described bysequentially drawing and false twist texturizing a synthetic yarnwherein the yarn is withdrawn from the texturizing zone at a greaterspeed than it is fed thereto. in a preferred embodiment, the draw rollfor the drawing step also serves as the take-off rollfor the texturizingzone and is stepped so that the portion used to take off the texturizedyarn is of greater diameter than the part used for drawing. A furtherpreference is that the heater in the texturizing zone is a heated pin.

15 Claims, 2 Drawing Figures PAIENTEUAUBIBW 3.828.537

SHEET 2 OF 2 ind o x 'NCREASE SPEED SPEED AFTER DRAWING MIGIQIU dWIMC)PRODUCTION OF TEXTURISED YARN The present invention relates toimprovements in or relating to the production of texturised yarn. Inparticular the present invention is concerned with the production oftexturised yarn by the false twist principle. False twisting is atechnique which is used to produce a texturised effect in yarns and afalse twist is conveniently acheived by first passing a moving yarnthrough a region where it is heated to above the second order transitiontemperature of the materials from which the yarn is made then allowingthe yarn to cool and twisting the cooled yarn. The twist imparted to thecooled yarn runs back along the yarn in the opposite direction to thatin which it is travelling and into the heating zone so that the twist isset in the yarn when it moves into the cooling zone and the temperaturedrops below the second order transition temperature.

After the yarn has passed through the twisting device, it is allowed tountwist so that the untwisting of the yarn which has been set in itstwisted state results in a texturised or bulked yarn.

Many fabrics require a high level of bulk in the yarn particularlystretch fabrics as are used in ladies stockings. The bulk in fabric madefrom texturised yarn is mainly dependent on the twist density of theyarn in the heating zone. By twist density we mean the number of twistsper unit length in the yarn. Twist density is controlled by the natureand physical properties of the yarn supplied, ie, its chemical type,titre, number of filaments in the cross section and by the physicalproperties of the filaments, and also by the imposed processingconditions, namely yarn'speed, twist speed, time and temperature ofheating and cooling, frictional forces in the twisting device and thenature and amount of lubricant on the surface of the yarn. It has beendifficult to produce texturised yarn capable of developing a constanthigh level of bulk whilst having a low thermal shrinkage and an aim ofour invention is to provide such a yarn and a convenient method for itsproduction.

One problem that arises while texturising on a commercial scale is thatthe processing conditions tend to vary from one position on a machine toanother. This tends to result in non-uniform yarn which shows up asstripes in fabrics produced from the yarn for example the rings whichsometimes appear in ladies stockings. It is thought that thisnon-uniformity is at least partly due to inadequate contact between theyarn and both the heater and twist bush in the texturising zone whichresults in variations in the amount of twist inserted and the degree towhich the twist is set. It is an object of the present invention toimprove this uniformity.

Various devices are known for imparting twist to a moving yarn. In onesuch device the moving yarn is passed around a member which is providedwithin and rotates with a hollow spindle. In this way twist is insertedin the yarn as it passes through the spindle. This technique is limitedin the amount of twist that can be inserted in a yarn travelling at aparticular speed as it is only possible to insert one twist for everyrotation of the spindle. Alternative techniques for imparting twistwhich overcome this limitation use the friction principle whereby theyarn is twisted by contact with a rotating friction surface. The twistdevices which use the friction principle generally consist of rotatinghollow surfaces with which the moving yarn makes contact. In

some such devices the yarn passes through the cylindrical body whereasin others the yarn enters and leaves the body from the same side and isheld against the friction surface by a yarn guide.

The present invention is concerned with the production of texturisedyarn by the friction false twist principle because this allows a greaterdegree of twist to be inserted into the yarn for a given speed ofrotation of the twist bush and thus allows higher processing speeds tobe used. It has already been proposed to produce texturised yarn bysequentially stretching and texturising by using the same roll towithdraw the yarn from both the texturising and the stretching zones.However, in this earlier process the roll that is used is stepped andthe yarn passes around the portion of smaller diameter after passingthrough the texturising zone so that the yarn tension is relaxed whileit is passing through the texturising unit compared to its state in thestretching zone. We have found that this process results in yarn havinga non-uniform and comparatively low level of bulk. It has also beenproposed that yarn may be partially drawn and then simultaneouslytexturised and drawn to complete drawing. This process however suffersfrom the disadvantage that the yarn speed and the tension in the yarnduring texturising are fixed according to the required draw ratio andthus the process allows no freedom to control the yarn speed duringtexturising to ensure that the necessary degree of bulk is acheived.Furthermore, this process requires a comparatively high stretch in thetexturising zone which tends to remove some of the twist during heatingresulting in yarn having an undesirably low level of bulk. We have nowfound that providing certain conditions are used yarn having a desiredhigh level of bulk as shown by its crimp rigidity may be obtained.

The present invention therefore provides a process for the production oftexturised yarn wherein thermoplastic synthetic yarn is sequentiallystretched and texturised by the friction false twist principle ashereinbefore described wherein the yarn is fed continuously from thestretching zone to the texturising zone and the yarn leaves thetexturising zone at a greater speed than that at which it enters thesaid texturising zone.

It is to be understood that the present invention is concerned only witha process where the increase in speed in the texturising zone iscomparatively small and is not of the same order as speed increasesgenerally used for stretching yarn. Whilst the actual speed increaseused depends upon the particular yarn we generally fmd that it should beno greater than a 10% increase.

The process of the present invention may be applied to the production ofyarn from any thermoplastic synthetic material which when twisted at atemperature above its second order transition temperature and thencooled whilst in its twisted state becomes set in that twisted state.Examples of particularly useful thermoplastic synthetic materialsinclude Nylon 6, Nylon 6.6, polyacrylonitrile and thermoplasticpolyesters such as polyethylene terephthalate.

In our preferred process the unstretched yarn first passes from a feedstation to a draw roll so that the yarn is stretched between the feedstation and the draw roll. The yarn is then fed directly from the drawroll through a heater zone which we prefer be a pin heater around whichthe yarn is wrapped as this ensures quick heating and uniform heattransfer between the yarn and the heater and allows higher speedprocesses to be used. It is thought that the techniques of the presentinvention are particularly suited to processes using a pin heaterbecause the slight increasse in yarn speed in the texturising zoneensures good contact between the yarn and the pin heater to giveconsistent heating in addition to good contact between the yarn and thefriction bush to give a more constant level of twist. A furtheradvantage of using a pin heater is that the extent to which the yarn isheated may readily be altered by varying the wrap of the yarn around theheater. In addition a pin heater has the added advantage that itoccupies considerably less space for the same degree of heating than theplate heaters traditionally used in processes of this type. If theincrease in speed in the texturising zone is too great some of the bulkinserted by the bush will be pulled out by the high tension. If,however, there is a reduction in yarn speed during texturising the yarnwill not be held sufficiently firmly against the friction bush to impartadequate twist to the yarn nor against the heater to ensure adequatesetting of the twisted yarn. After the yarn has passed the heater it iscooled to ensure that it is cold when it reaches the twist device, andit may be necessary to provide cooling plates which direct cold air onto the yarn, but generally we find it more convenient to ensure that thedistance the yarn travels between the heater and the twist device issufficient to cool the yarn.

After cooling the yarn passes to the twisting device which may be any ofthe known friction devices for imparting twist to yarns, in particulartwist bushes. The twist imparted to the yarn runs back along the yarn tothe heater so that the yarn is twisted when hot and the hot twisted yarnthen cools thus setting the yarn in its twisted state. According to thefriction false twist technique the twist device provides a rotatingfriction surface with which the yarn is brought into contact so that therotation of the friction surface imparts a twist to the yarn. The yarnis withdrawn from the twist device in such a way that the speed ofwithdrawl is greater than the speed of the yarn as it is fed to thetwist device. In a preferred embodiment the yarn is withdrawn from thetwist device by the roll that is used as the draw roll of the stretchingzone. In this particular technique, the roll is stepped so that theportion around which the yarn passes at the end of the draw zone is ofsmaller diameter than the portion around which the yarn passes after thetexturising zone so that the speed of the yarn is increased between thetwo portions of the roll. This technique is preferred as the dualfunctions of a single roll results in a more compact aparatus.

The preferred amount by which the yarn speed should be increased in thetexturising zone depends upon the nature, denier and amount of twisttobe inserted into the yarn. However, we have found that for certain yarnsthere are limits for the speed increase within which the desired highcrimp rigidity is obtained. We find that these limits are generallywithin the elastic limit of the yarn and thus our process usuallyresults in no permanent stretch of the yarn as it passes through thetexturising zone over and above any stretch imparted by the texturisingaction. This is apparent by a comparison of the average decitex of theyarn produced by our preferred process with the average decitex of yarnproduced by a similar process without any speed increase in thetexturising zone which shows virtually no difference in the decitex ofthe two yarns.

However, in some instances the increase in speed may be such as toresult in a slight permanent stretch but this is generally very small.The preferred increase in yarn speed depends upon the particular type ofyarn. However, we have found that a speed increase between 2 and 10% isto be preferred. In particular, we find that an increase in yarn speedof between 2 and 6% is suitable for the production of texturisedpolyamide yarn. A speed increase of this magnitude during texturisingproduces virtually no more permanent stretch than a similar process withno such speed increase.

After the yarn has been withdrawn from the texturising unit, it is fedto the wind-up. We have found that the process of the present inventionenables a yarn of high crimp rigidity to be obtained which isparticularly important for yarns to be used in fabrics where fabric bulkand high elasticity are required such as for example in ladiesstockings. In addition the yarns produced by our process have asufficiently low shrinkage that a fabric made from the yarn does notalter appreciably during fabric finishing. We have also found that theslight speed increase in the texturising zone results in improvements inboth the uniformity of the yarn obtained from one position on a machineand between the yarns obtained from different positions. This is thoughtto arise from greater yarn stability and in some instances it ispossible to see that the threadline is more stable during texturisingthan in similar processes with no speed increase during texturising.This improved stability also leads to a smoother running process shownby the fact that threadline breaks occur less frequently when using theprocess of the present invention.

The crimp rigidity of a yarn is a measure of the ability of a texturisedyarn to develop bulk during finishing and of the ability of the yarn toretain the bulk. The higher the crimp rigidity the greater the degree ofbulk and the more elastic the yarn. For the purposes of thisspecification crimp rigidity is determined by making a loop from thetexturised yarn and initially hanging a weight of 0.1 grams per decitexon the yarn and suspending the weighted skein in water at 20 C for 2minutes. The length of the skein is then measured. The weight is thenreplaced by a weight of 0.002 grams per decitex and the length of theskein measured under similar conditions. The crimp rigidity is the ratioof the length under a load of 0.002 grams per decitex to the lengthunder a load of 0.1 grams per decitex expressed as a percentage. Inparticular, by using the process of our invention we have obtained yarnhaving a crimp rigidity of from 35% to 50% and a shrinkage of less than5%; the crimp rigidity that may be achieved is of course dependent onthe decitex of the yarn.

In a preferred embodiment of the present invention a twist dammingelement is positioned in the yarn path between the draw roll and theheater. The term twist damming element refers to any system whichprevents twist running along a yarn and may be a pin around which theyarn is wound although this is not preferred as such a dramatic changein yarn direction can cause filamentation and damage to the yarn. We dotherefore prefer to use a system in which the direction of the yarn pathis changed as gradually as possible consistent with achieving thenecessary degree of twist damming. We have found that a particularlyuseful twist damming element comprises a series of yarn guides which arepreferably rolls or ceramic guides around which the yarn passes whereinthe yarn path is forced to change by at least 75 as it passes aroundeach roll. We find the inclusion of a twist damming element useful as itprevents the twist inserted by the twist device from running back ontothe draw roll. If the yarn is twisted on the draw roll an inferiorproduct can result as tension fluctuations in the draw zone can occurgiving rise to non-uniform drawing and a variable product. Furthermore,the yarn tends to roll on the surface of the roll so that adjacentstrands become intertwined, thus stopping operations. In addition if theyarn moves on the surface of a roll which controls yarn speed due to thetorque imparted by texturisation the surface of the roll becomes quicklydamaged. The use of a twist damming element has an added advantage whenused in conjunction with a pin heater as if the damming element is amovable yarn guide its position may readily be altered to provide anyeasy method of varying the wrap of the yarn around the pin heater.

The essence of our invention is therefore a continuous stretching andtexturising process in which the yarn speed is increased duringtexturising. It should be understood that this principle may be appliedto a process in which the yarn is first simultaneously stretched andtexturised and then subsequently further texturised. In this embodimentthe speed of the yarn will be increased during the further texturising.Similarly the texturised yarn produced by our process may be furthertexturised if required. Both these processes are aimed at ensuring evengreater uniformity of the final bulked yarn.

The yarn produced by the process of this invention is a torque yarn asit has been twisted in one direction about its axis. However, if atorque free yarn is required, our process may be applied to two separateyarns which pass through the apparatus in parallel and are subjected toequal amounts of twist but in the opposite direction. The yarns may thenbe combined to form a torque free composite yarn.

The present invention also provides an apparatus for sequentiallystretching and texturising yarn comprising a draw zone with feed meansand a drawing means and a texturising zone comprising a feed roll, aheater, a friction texturising device and a withdrawing means whereinthe feed roll also acts as the withdrawing means for the texturisingzone and is stepped so that it is the portion of larger diameter thatacts as the withdrawing means. I

The various modifications and. embodiments of the apparatus of thepresent invention corresponds to the embodiments of the process alreadydescribed.

The present invention is illustrated but in no way limited by referenceto the accompanying diagrammatic drawing FIG. 1. Undrawn yarn l isdelivered to feed roll 2 from which it passes to the draw pin 3 and thend aw ol ..5-,Tbe. raw..ro 51 pa a d the y justed so that the yarn isstretched to the desired extent. After passage around the portion 6, theyarn passes to heated pin 7 where it is heated to a temperature abovethe second order transition temperature of the material from which theyarn is made. The yarn then passes to yarn guide 8 and into the frictiontwist bush 9. The yarn path between the heated pin 7 and the pin guide 8is sufficiently long to ensure that the yarn is no longer tacky when itpasses through the guide 8.

In the type of twist bush illustrated, the yarn passes through the bushand it is twisted by frictional contact between the inner surface of thebush and the yarn. The twist imparted to the yarn runs back along theyarn towards the heated roll 7 so that the yarn is twisted while hot andthe twist is set in the yarn as it cools. The yarn passes from the twistbush through another yarn guide 10 to the larger diameter portion 11 ofthe roll 5. From the portion 11, the yarn travels around the separatorroll 4, back to the portion 11 of roll 5, back to the separator rollagain, through the yarn guide'8 and is wound up on the bobbin 12 bymeans of the ring and traveller 13; Thus, the speed of the yarn isincreased as it passes through the texturising zone because it is fed tothe zone at the peripheral speed of the smaller portion of roll 5 and iswithdrawn at the peripheral speed of the larger portion.

The presentinvention is further illustrated but in no way limited byreference to the following examples throughout which any reference tothe decitex of the yarn refers to the decitex after texturising.

EXAMPLE I Twenty-two decitex 7 filament Nylon 66 yarn was processedusing the apparatus illustrated in FIG. 1. The draw roll 5 was driven sothat the portion of smaller diameter 6 was rotating at a peripheralspeed of 685 metres per minute to draw the yarn to a ratio of 2.66. Thetwist bush 9 was rotated at a speed of about 21,500 revolutions perminute and the heated pin 7 was maintained at a temperature between 220and 230C. the roll 5 was stepped so that the peripheral speed of thelarger portion 11 was 4% greater than that of the smaller diameterportion 6.

For the sake of comparison, an identical sample of yarn was processed inexactly the same manner with the exception that after passage throughthe textu rising zone, the yarn did not pass over the larger diameterportion of roll 5 (ie. portion 11) but passed once again over theportion 6 so that the yarn was not subject to any increase in speedduring texturising.

The properties of the two yarns obtained are set out in the followingtable:

With 4% increase in yarn With no speed increase speed in tcxturisingzone from the draw pin 3 passes to the portion 6 which has the smallerdiameter. The yarn then travels to the separator roll 4 and again to theportion 6. The relative speeds of the feed roll 2 and the draw roll 5are ad- Thus it may be seen that by employing the process of the presentinvention, yarn having an improved crimp rigidity and a lower shrinkagemay be obtained without impairing other yarn properties. The yarn wassubsealtsivs sssf u quently knitted into stockings which after dying andfinishing had excellent appearance and uniformity.

The hot shrinkage of the yarn is determined by taking a 1 metre lengthof yarn that has been stored for at least 24 hours under normalconditions. The length of yarn is made into a single loop and subjectedto a tension of 18 grams/decitex and the length of the loop measured (LThe loop of yarn is then suspended in boiling water for minutes, driedunder normal conditions for 24 hours, re-subjected to a tension of 18grams/- decitex and the length of the loop measured (L The percentageshrinkage is given by (L L )/l.. X 100.

The crimp rigidity of the yarn is measured by the technique previouslydescribed.

EXAMPLE n v The process of Example 1 was repeated but using a 44 decitex14 filament polyamide yarn and a twist bush speed of 12,500 revolutionsper minute. Several runs were carried out in which the speed at whichthe yarn was withdrawn from the texturising zone compared to the speedat which is was drawn off from the draw zone was varied from 6% belowthat at which it was withdrawn from the draw zone to 10% above that atwhich it was withdrawn from the draw zone. The crimp rigidity of eachsample was measured by the method described above and FIG. 2 is a plotof crimp rigidity against the amount by which the yarn speed isincreased through the texturising zone. As may be seen the curve passesthrough a peak at about 4% increase in speed.

EXAMPLE Ill The process of Example I was repeated using a 3 filament l7decitex polyamide yarn. The draw roll 5 was 7 driven so that the portionof smaller diameterwas ro- Speed Change of Yarn Accordingly it may beseen thatin all instances the process of the present invention producedyarn of improved crimp rigidity. In addition these results show that thespeed increase results in a higher yarn tension before the heater whichgives rise to improved running.

EXAMPLE IV The process of Example I was repeated using a 3 filament 17decitex polyamide yarn. The portion of the draw roll which withdraws theyarn from the draw zone was rotating at a peripheral speed of 674 metresper minute and the roll was stepped to give an 8% increase in speedbetween the beginning and the end of the texturising zone. Thetemperature of the heated pin was about 230 C and the yarn thread up wassuch that the yarn passed once around the pin. The yarn obtainedcontained 7,100 twists per metre, had a crimp rigidity of 41.5% and ashrinkage of 5.3%. Tension measurements on the yarn during processingshowed that the tension before the heater was 2.4 grams, immediatelyafter the heater it was 6.8 grams and after the twist bush 12.5 grams.

As may be seen in Examples 111 and IV the increase in the speed of theyarn in the texturising zone results in an increase in yarn tensioncompared to a similar process with no speed increase during texturising.It is this increase in tension which is thought to result in moreuniform running and few yarn breaks because yarn has a tendency to stickto the processing rolls which can result in fluctuations of theconditions to which the yarn is subjected and this tendency is reducedby the higher tensions we produce. Our invention therefore provides asimple method of overcoming this disadvantage. Tension measurements werealso made during the production of 14 filament 44 decitex polyamide yarnpassing round a 4 inch diameter pin heater held at a temperature of 230C; the results were as follows:

Tension in Yarn (grams) in Texturising Zone Speed Decreased by 4% NoChange Speed Increased by 4% Before heater Between heater After twistand twist bush bush The yarn produced by the process involving a 4%increase in speed produced more uniform fabrics and also ran much moresmoothly during texturising than the other yarns.

The increase in tension before the heater is important when a pin heateris used as the wrap of the yarn around the pin heater reduces the yarntension before the heater and there is a risk that the tension willbecome so low that the yarn will occasionally stick to the roll thatfeeds it to the texturising zone. Our invention Bush Speed CrimpRigidity (7r) Shrinkage (7c) Yarn Tension (grams) With 4% Without With47: Without With 4% Without speed 4% speed speed 4% speed speed 4% speedr.p.m. increase increase increase increase increase increase provides acomparatively simple method of overcoming this problem.

We claim:

1. A process for false twist texturing a synthetic filament yarncomprising sequentially passing the yarn being treated through a drawingzone, a twist heat setting zone, a twisting zone, an untwisting zone anda yarn speed increase zone prior to take up wherein the yarn is firstdrawn to the desired extent prior to passing to the twist heat settingzone and twisting zone, said yarn being twisted and the twist beingpassed upstream into the twist heat setting zone wherein said yarn isheated to above its second order transition temperature to set said yarnin the twisted configuration, untwisting said heat set yarn, increasingthe speed of said yarn up to about percent as it passes through saidheat setting and twisting zone and subsequently taking up a texturizedyarn.

2. The process of claim 1 wherein the yarn is a polyester continuousfilament yarn.

3. The process of claim 1 wherein the yarn is a polyamide continuousfilament yarn.

4. The process of claim 1 wherein the yarn speed increases as it passesthrough said heat setting and twisting zone by 2 to 10 percent.

5. A process according to claim 4 in which the yarn speed increases bybetween 2 and 6%.

6. A process according to claim 1 in which the increase in speed in theyarn as it passes through the heat setting and twisting zone is suchthat it produces no permanent stretch in the yarn.

7. The process of claim 1 wherein the yarn passes through a twistdamming zone prior to passing through said twist heat setting zone.

8. The process of claim 7 wherein the twist damming zone comprisespassing the yarn through a path of'cun vature equalling at least a turn.

9. A process according to claim 1 in which the yarn is also texturisedin the stretching zone.

10. A process according to claim 1 in which the texturised yarn isfurther texturised.

11. An apparatus for sequentially stretching and texturising yarncomprising a draw zone with means for feeding the yarn to a texturisingzone and drawing means to withdraw the yarn from said texturising zoneand to effect the required drawing of the yarn and said texturising zonecomprising a feed roll, a heater, a friction texturising deviceproviding a friction surface which bears against the yarn and a meansfor withdrawing the yarn wherein the feed roll also acts as thewithdrawing means and is stepped so that it is the portion of largerdiameter which acts as the withdrawing means.

12. An apparatus according to claim 11 in which the heater in thetexturising zone is a heated pin with which the yarn makes contact.

13. An apparatus according to claim 11 in which the feed roll for thetexturising zone is also the drawing means for the draw zone.

14. An apparatus according to claim 11 in which the diameter of theportion of the feed roll is between 2% and 10% larger than the otherportion of the roller.

15. An apparatus according to claim 11 including a twist damming elementwith which the yarn makes contact between the heated pin and the drawroll.

1. A process for false twist texturing a synthetic filament yarncomprising sequentially passing the yarn being treated through a drawingzone, a twist heat setting zone, a twisting zone, an untwisting zone anda yarn speed increase zone prior to take up wherein the yarn is firstdrawn to the desired extent prior to passing to the twist heat settingzone and twisting zone, said yarn being twisted and the twist beingpassed upstream into the twist heat setting zone wherein said yarn isheated to above its second order transition temperature to set said yarnin the twisted configuration, untwisting said heat set yarn, increasingthe speed of said yarn up to about 10 percent as it passes through saidheat setting and twisting zone and subsequently taking up a texturizedyarn.
 2. The process of claim 1 wherein the yarn is a polyestercontinuous filament yarn.
 3. The process of claim 1 wherein the yarn isa polyamide continuous filament yarn.
 4. The process of claim 1 whereinthe yarn speed increases as it passes through said heat setting andtwisting zone by 2 to 10 percent.
 5. A process according to claim 4 inwhich the yarn speed increases by between 2 and 6%.
 6. A processaccording to claim 1 in which the increase in speed in the yarn as itpasses through the heat setting and twisting zone is such that itproduces no permanent stretch in the yarn.
 7. The process of claim 1wherein the yarn passes through a twist damming zone prior to passingthrough said twist heat setting zone.
 8. The process of claim 7 whereinthe twist damming zone comprises passing the yarn through a path ofcurvature equalling at least a 75* turn.
 9. A process according to claim1 in which the yarn is also texturised in the stretching zone.
 10. Aprocess according to claim 1 in which the texturised yarn is furthertexturised.
 11. An apparatus for sequentially stretching and texturisingyarn comprising a draw zone with means for feeding the yarn to atexturising zone and drawing means to withdraw the yarn from saidtexturising zone and to effect the required drawing of the yarn and saidtexturising zone comprising a feed roll, a heater, a frictiontexturising device providing a friction surface which bears against theyarn and a means for withdrawing the yarn wherein the feed roll alsoacts as the withdrawing means and is stepped so that it is the portionof larger diameter which acts as the withdrawing means.
 12. An apparatusaccording to claim 11 in which the heater in the texturising zone is aheated pin with which the yarn makes contact.
 13. An apparatus accordingto claim 11 in which the feed roll for the texturising zone is also thedrawing means for the draw zone.
 14. An apparatus according to claim 11in which the diameter of the portion of the feed roll is between 2% and10% larger than the other portion of the roller.
 15. An apparatusaccording to claim 11 including a twist damming element with which theyarn makes contact between the heated pin and the draw roll.